Origins And Microbiology Flashcards
What did replication likely begin with?
What would the very first cells have been?
What is a fundamental requirement for cells?
RNA as the genetic material, evolving to eventually use DNA.
Prokaryotic cells.
Energy is fundamental for cells.
Define life?
The organism must be made of units that reproduce by division, these properties are inherited by offspring. There also must be random mutations that retain a variation among offspring.
Describe some features of the Earth’s biome 3.5 billion years ago.
There was considerable microbial diversity. All life was prokaryotic. Some cells may have used photosynthesis to produce carbon organic compounds from the surroundings. No cells ate one another- very basic food chains. They all competed for the same basic resources.
What was oxygen originally produced as? How was it used up?
What were the seas like 3.5bya?
It was produced as a waste product, it was consumed through the oxidation of reducing compounds such a a ferrous iron.
The seas were anaerobic.
What event occurred which allowed proto-eukaryotes to respire oxygen?
What is the minimum age of the eukaryotes?
What is the minimum age of plants?
Endosymbiosis.
- 45 billion years (minimum age for eukaryotes),
- 2 billion years (minimum age for plants).
What percentage of the today’s oxygen levels do aerobic bacteria need?
How much do eukaryotes need?
How much do multicellular organisms need?
1%
1-2%
10%
What was the final earth development stage needed before organisms could colonise the land?
Formation of an ozone layer.
Phylogenetic relationships shown in the tree of life are based on data from what?
What does the tree of life not show?
16S and 18S rRNA sequencing.
It does not show phenotypic complexity.
If the biodiversity of the Phanerozoic era is looked at, a number of dips in biodiversity can be seen. What are these dips?
One of these dips occurred around 63 million years ago. What occurred?
Major extinction events. There have been five major extinction events.
63 mya the great Cretaceous extinction event occurred, dinosaur life was reduced to near zero.
What evidence is there to support a bolide collision of earth 63mya?
An iridium layer in rock formations.
Shocked quartz.
The chicxulub crater in the Gulf of Mexico.
What are the two types of extinctions?
Background extinctions and mass extinctions.
Background extinctions are the natural rate of extinction in the earths geological and biological history before humans became a primary contributor to extinctions. A mass extinction is a widespread and rapid decrease in the amount of life on earth.
What are the common features of a mass extinction?
One group of organisms replaces another.
Small animals survive, large ones don’t.
Weed species are more likely to survive.
Some groups have their competitors removed.
Acceleration of the replacement of one group by another
Some taxa are completely unaffected.
Cyanobacteria have left a fossil record that dates back to when?
They form large layered structures called?
They have left fossil records that date back to the Precambrian, the oldest fossils being nearly 3.5bya.
They form large layered structures called stromatolites.
Name the bacteria involved in the nitrogen cycle and briefly describe their role.
Rhizobium- involved in nitrogen fixation of nitrogen gas into root nodules of leguminous plants.
Nitrosomonas- involved in nitrification. It oxidises ammonia into nitrite.
Nitrobacter- involved in nitrification. It oxidises nitrite into nitrate.
Pseudomonas- these are involved in dentrification, this is the use of nitrate as terminal e- acceptors in respiration.
Name how bacteria are used in industry.
Enzymes for washing powders are produced by bacillus species. Some enzymes produced by these bacteria are used in the food industry.
Brevibacterium flavin is used in the production of amino acids, such as aspartic acid for aspartame.
Pseudomonas is used in the production of vitamins.
Describe how bacteria are used in agriculture?
Rhizobiaceae is a bacterium that fixes nitrogen for leguminous plants. It has a symbiotic relationship with legumes residing within their root nodules. Many bacteria are plant pathogens (Agrobacterium) and can be used weed killers. Additionally bacteria can be used as biological pesticides. They are also used in silage production.
Describe how bacteria are used in genetics.
Escherichia coli is a model organism in genetics. Also restriction enzymes gained from bacteria are used in molecular biology to cut DNA.
Furthermore Taq polymerase is an enzyme obtained from Thermophillus aquaticus.
Describe how bacteria are used in medicine.
Many bacteria species are responsible for the array of antibiotics we possess to treat bacterial pathogens. Streptomycces is one genus of bacteria that has contributed many antibiotics to the list.
Describe how bacteria are used in food production.
Lactobacillus is used in the production of yoghurt. Also vinegar is the result of converting ethyl alcohol to acetic acid by acetic acid bacteria (members of the genera acetobacter and gluconobacter).
What are the two prokaryotic domains?
The eubacteria and the archaebacteria.
What are the eubacteria? What are used characteristics are used to classify them?
These are prokaryotic organisms, their classification depending on their phenotype. Their cell shape and morphology, methods of energy production and gram staining being classifying methods.
What are the four bacterial cell shapes?
Bacilli (rod) example: E. coli
Cocci (spherical) example: streptococcus
Filaments example: S. griseus
Spirilla (curved walls) example: V. cholera
What are the three methods of energy production?
Aerobic- organisms grow in the presence of oxygen which acts as a terminal electron acceptor.
Anaerobic- organisms grow in the absence of oxygen with alternative electron acceptors being used.
Fermentation- organisms grow in the absence of oxygen where an internal organic molecule such as glucose is the electron donor and terminal electron acceptor.
